Keywords: 
• benzimidazole /
• density functional theory (DFT) /
• acute toxicity /
• electrotopological state index /
• quantitative structure-property/activity relationship(QSPR/QSAR)

Abstract: Theory of density function (DFT) was used to calculate the quantum chemical parameters such as orbital energy (E_NHOMO, E_NLUMO), energy gap of them(ΔE₂), atomic charge (Q), and the thermodynamic parameters such as thermal correction value (E_th), heat capacity at constant volume (C_v^φ), standard entropy (S^φ), and electrotopological state index (E_m) of eight compounds based on 1-replaced-2-amino benzimidazole at B3LYP/6-31G (d) level. Two models of quantitative structure-activity relationships (QSAR) about toxicity of the compounds and three models of quantitative structure-property relationships (QSPR) about thermodynamic property of them were established by the leaps-and-bounds regression analysis respectively. Correlation coefficients R² of the models and R_cv² based on leave-one-out (LOO) cross validation were greater than 0.84 and 0.72 respectively. Deviations between calculated values and predicted values of lgLD50 were 0.11 and 0.20 respectively, and relative mean error between calculated values and predicted values of E_th,C_v^φ and S^φ were 3.89%、4.03% and 2.64% respectively, which exhibited a good robustness and good prediction capability. The results of our research have revealed effect of groups on toxicity. Therefore, it would facilitate to assess hazard of the compounds based on 1-replaced-2-amino benzimidazole in environment, and provide theoretical foundation for research and development of new drugs with high efficiency and low toxicity based on benzimidazole.